Time switch



May 3, 1955 w. P. GALLAGHER ETAL 2,709,341

` TIME SWITCH Filed Apr-11 21, :1.951

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TIME SWITCH Filed April 2l, 1951 5 Sheets-Sheet 2 rw :wm M0705 May 31? i955 w. P. GALLAGHER ET AL 2,709,341

TIME SWITCH Filed April 21, 1951 5 Sheets-Sheet 3 T0 TIMER Mf? May 31, 1955 w, p, GALLAGHER ETAL. 2,709,341

TIME SWITCH Filed April 2l, 1951 5 Sheets-Sheet 4 @.267 A 7g j; 4921 L if?? L INI THERMAL OVERLOD .5W/76H H gig/#127.5 /NVENTOR5:

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TIME` SWITCH 5 Sheets-Sheet 5 Filed April 2l, 1951 United States Patent hice Patented May 3l, "i955 TME SWITCH William P. Gallagher, Anthony D. Stolle, and Paul G. Bieliir, Chicago, Ill., assignors to International Register Company, Chicago, Ill., a corporation of Illinois Application April 21, 1951, Serial No. 222,238 15 Ciaims. (Cl. 62-4) This invention relates to time switches, particularly of the type for use in temporarily changing the operative condition of electrical circuits so as to control the operation of alternate mechanisms, such for example as is required to effect the regular, accelerated defrosting of refrigerators.

As is well known, in refrigerators, and especially in those in domestic and limited commercial use, the refrigerant plates become coated with an increasingly thick layer of frost. In order to insure an effective operation of the refrigerator this coating of frost has to be removed periodically. Heretofore this generally has been effected by simply turning off the refrigerant generator and allowing it to remain idle until there was a sufficient rise in temperature of the refrigerant to cause a dissipation of the frost or such a loosening thereof as to permit its removal. Obviously, the time and duration of such a defrosting is at the discretion and convenience of an attendant. Some one has to remember to turn off the refrigerant generator, to estimate the duration of its idleness, and remember to turn the generator on again. Moreover, such a procedure of defrosting generally has to be done during a time when some attendant is available and has to be undertaken when access to the refrigerator is not required-or at least not too frequently. Such an attendant-controlled operation involves the objection of the defrosting not being done frequently enough to assure the most efficient operation of the refrigerator and/or the hazard of over-extending the period of defrosting with the consequence of possible food deterioration.

Recently, timers have been provided frosting period may be automatically effected at regular intervals. However, they have been confined to merely turning oi and on the operation of the refrigerant compressor. Presently means are being provided to so modify the cold condition in the evaporator as to accelerate the defrosting operation. This is being done either by heating the evaporator plates by means of an electric heating coil or influencing the refrigerant iiow.

The main objects of this invention, therefore, are to provide an improved form of time switch particularly suited for use in temporarily changing the iiow of current from one circuit to another; to provide an improved switch of this kind particularly adapted for controlling the periodic immobilization of the refrigerating mechanism and the concurrent operation of the means for accelerating the defrosting of the refrigerant coils; to provide improved means for making the restoration of normal operation of the time switch dependent upon the condition of defrosting action; to provide a time switch of this kind whereby this dehaving improved means for effecting a quick make and break of the requisite electrical contacts for the alternate circuits required for the functioning of such mechanism and means; to provide a time switch of this kind having improved means for effecting the simultaneous or the sequential making and breaking of the aforesaid multiple circuits as circumstances may require; and to provide an improved time switch of this kind which involves the minimum of moving parts, hence being simple and economical to manufacture, positive in operation, and capable of use over extended periods of time without attention or the necessity of servicing, repair, or replacement.

Various adaptations of a time switch embodying this invention are shown in the accompanying drawings wherein:

Fig. l is a reduced elevationai View illustrating in general how any of the time-switch adaptations shown in the drawings, with its indicating pointer for manual adjustment, might be arranged with respect to a minimum scale on a surrounding refrigerator housing for guiding the setting of the switch so that it will always defrost the refrigerator at the predetermined time for which the synchronous motor has been designed;

Fig. 2 is a front elevation of a simplest kind of adaptation of this invention, as arranged on an insulating panel for use with a (typical) make of refrigerator for the purpose of temporarily changing the ow of current from the circuit controlling the refrigerating mechanism to a circuit controlling means for accelerating the defrosting of the refrigerator, the circuit-making and -breaking switch-operating means being shown in position for closing the circuit to the refrigerating mechanism;

Fig. 3 is a partial view of the same showing the circuitmaking and -breaking means in its position for temporariiy reversing the condition of the circuits so as to initiate the defrosting operation;

Fig. 4 is a vertical, sectional, elevation of the adaptation taken on the line 4 4 of Fig. 2;

Fig. 5 is a side elevation of the mechanism as viewed from the left of Fig. 2;

Fig. 6 is an elevational View of one of the posts whereby the switch contacts or switch arm are secured to a mounting, before the post is staked to the mounting;

Fig. 6-A shows such a post after it has been staked to the mounting;

Fig. 6-B is a plan view of the same;

Fig. 6-C is a fragmentary detail of the switch mechanism taken on the line 6-C 6G of Fig. 3;

Fig. 7 is a circuit diagram showing the switch mechanism arranged in the power circuits leading to the refrigerating mechanism and the defrosting means;

Fig. 8 is a front elevation view (with housing cover removed) of a slightly different arrangement of the switch and its operating mechanism embodying this invention, for use with another typical make of refrigerator, the switch and its operating mechanism being shown in position for closing the circuit to the refrigerating mechanism;

Fig. 9 is a similar view but showing the switch and its operating mechanism in reversed position, for opening the refrigerating mechanism circuit and closing the circuit to the defrosting means;

Fig. l() is a side elevation of the mechanism shown in Fig. 8 one corner being broken away to more clearly show the cover mounting and internal construction;

Fig. ll is a vertical cross sectional view of the same taken on the line ift- 11 of Fig. S;

Fig. l2 is a circuit diagram showing the switch mechanism arranged in the power circuits leading to the refrigeratiug mechanism and the defrosting means;

Fig. 13 is a front elevational view of another adaptation, similar to that shown in Fig. 8, but supplemented with a solenoid, whereby the return of the switch means to close the circuit to the refrigerating mechanism is controlled by the condition of the refrigerant plates;

Fig. 14 is a View of this switch means and its operating mechanism after being shifted by the cam, and shown as being held in shifted position by the action of the solenoid;

Fig. is a side view of this adaptation taken from the right of Fig. i3, the housing being in section;

Fig 16 is a vertical sectional detail taken on the line 1.6-16 of Fig. 13;

Fig. 17 is an enlarged fragmentary detail showing how the cam and cam shaft of this switch-operating mechanism are formed and assembled to permit a slight relative angular movement between said cam and cam shaft;

Fig. 18 is a cross sectional detail of the same taken on the line -i of Fig. 17;

Fig. 19 is a circuit diagram showing this particular adaptation of switch means arranged in the circuits leading to the refrigerating mechanism and the defrosting means, the switch being shown held in defrosting position by the solenoid;

Fig. 20 is a front elevation of a further adaptation of this improved time switch showing auxiliary means for effecting a delayed action of the closing of the circuit to the refrigerating mechanism after the circuit to the defrosting means has been opened, the switch and switchoperating mechanism being shown in their respective positions after the switches have been shifted to open the circuit to the refrigerating mechanism and close the circuit to the defrosting means;

Fig 21 is a similar view but showing the switches and the switch-operating mechanism in their reversed positions;

Fig. 22 is a right-hand side elevation of the adaptation shown in Fig. 20;

Fig. 23 is a transverse sectional View taken on the plane of the line 2.3-23 of Fig. 20;

Fig. 24 is a circuit diagram showing this particular switch adaptation arranged in the power circuits leading to the refrigerating mechanism and the defrosting means, the switch being in defrosting position;

Fig. 25 is a still further adaptation of this improved type of time switch for use with a typical make of refrigerator employing a form of defrosting means different from that illustrated in the previous figures;

Fig. 26 is a right-hand side elevation of the same;

Fig. 27 is a sectional elevation of the same taken on the line 27-27 of Fig. 25; and

Fig. 28 is a circuit diagram of this adaptation arranged in the power circuits leading to the refrigerating mechanism and a form of derosting acceleration involving the use of the refrigerant uid.

The distinctive concept of this invention involves a motor-driven cam for oscillating a control member connected to one or more spring-actuated, over-center-acting switches for individually and simultaneously or sequentially controlling circuits which determine the alternate functioning of the refrigerating mechanism and the defrost accelerating means, the oscillating control member, for certain situations, having associated therewith means for making the closing of the circuit for the refrigerating mechanism conditioned upon factors other than those which cause the opening of that circuit and the closing or" the circuit to the defrost accelerating means.

A time switch embodying this concept comprises a switch means A, the shifting of which is eiected by a switch-actuating mechanism B, driven by gearing C, and connected to a motor i), ali of which are arranged on a mounting E for suitable positioning on a refrigerator housing adjacent to an indicator scale F. As hereinbefore noted, such a time switch has been designed particularly for use in alternating the opening and closing of two circuits presently being employed in refrigerators to effect a periodic temporary idling of the refrigerating mechanism G and the temporary operation of a special, defrost accelerating means H or H. In the circuit diagrams shown in the drawings, and controlled by a time switch embodying this invention, the refrigerating mechanism G is represented by a square marked C. C. to indicate the usual cold control, and a round-ended elongated gure marked Comp to indicate the usual refrigerator compressor. The special defrost accelerating means H in the circuit diagram is indicated, in all but one, by the conventional representation for an electrical heating coil. in the one excepted diagram the defrost accelerating means H is indicated by a solenoid operated valve.

Where the defrost electrical heating coil is employed, it is necessary to preclude having the coil remain on longer than is needed to effect the defrosting operation, and also to insure that it will not remain on indenitely in case of switch failure. To that end a conventional bellows-operated switch, conditioned by the evaporator plates of the refrigerator, and a thermal overload switch, controlled by the food-compartment temperature, are included in the heating-element circuit, the precise functioning of which switches will be explained more fully later on.

The switch means A comprises one or two switch arms mounted for back and forth movement between pairs of oppositely spaced contacts 36 and 37. The arm or arms 35 and the contacts 36 and 37 are secured in a conventional manner to terminal posts 38 and 39 and dii, respectively, staked in a special way on the mounting E as will be explained presently. Such a switch means A is connected to control a pair of circuits leading respectively to the refrigerating mechanism G and the defrost accelerating means H or H. Whether one or two such switch means A are used will depend upon the desires of the refrigerator manufacturers. When two such switch means A are used, they usually are arranged in opposed relationship at opposite sides of the switch-actuating mechanism B. y

The special staking of these posts 38, 39, and 40, is indicated in Figs. 6, 6-A, and 6-B. Before assembly on the mounting E, the post-3S for exampleis formed of a iat piece or metal (see Fig. -B) with a shank 38a (see Fig. 6) between the stem Sb, whereon switch contacts or a switch arm are fixed, and the base part 38C, from which depends the connector part 38d. In width, this shank 38a is intermediate that of the contact stern 3811 and the base part 38C. The aperture 38e, formed in the mounting E (see Fig. 6-B) is greater than the thickness of the metal from which the post is formed but is shorter than the width of the shank 38a.

in assembling the post 3S (and the posts 39 and it?) on the mounting E the post is set in the aperture 33e with the shoulders 38f (see Fig. 6) resting on the mounting E. Thereupon a blow is struck against the end of the post 33 suiiicient to drive the shank 33a down through the mounting E, shearing oit the material below the shoulders 38j. Following this the shoulders are peened over the mounting E in the usual way, as shown in Fig. 6--A.

The switch-actuating mechanism B comprises a rocker arm 4i, a main cam 42 and, in certain adaptations, either a solenoid 43 (Figs. 13 and 14) or an auxiliary cam means 44 (Figs. 20 and 21) arranged to influence temporarily the action of the rocker arm di in one direction, independently of the main cam 4?..

rhe rocker arm el, employed in these several adaptations, is in the nature of a bell crank lever staked to a bushing 45 rotatably held by an E washer 46 on a stud shaft 47 staked to the mounting E. A spring 48 coiled around the bushing 4, with its ends respectively restrained by a stop pin 49 and hooked over the rocker arm 41, normally urges the rocker arm 41 to press a cam-track follower pin E@ against the main cam 42;, and when an auxiliary cam 44 is employed as in the adaptations shown in Figs. 20-24 to also press a cam-track follower pin 5l against the periphery of the cam 42 vhen the cam-track follower pin is in registration with the main earn offset 58.

The rocker arm il is connected to one or both switch arms 35 (depending upon whether one or two switch means A are used) by a U-shaped spring 52. The ends of the spring preferably are hingedly connected to the ends of the switch arms 35 and the rocker arm il so as to secure the freest possible action of the switch arm (or arms) 35 as inuenced by the oscillation of the rocker arm 41. Preferably, the ends ofthe springv 52 are provided with slots 53 (see Fig. 6-C) in which are seated tongues 54 formed on the ends of the switch arm 35 and the rocker arm 41. As shown in Fig. 2, the tongue 54 on the rocker arm 41 may be an integral extremity of the rocker arm 41 or switch arm 35 or, as shown in other figures, the tongue 54 may be formed on a flat piece 55 forced into and staked on the rocker arm 41 in the same way as hereinbefore explained with regard to the switch post 38.

The axis of the rocker-arm stud-shaft 47 generally is so positioned with respect to the attachment of the switch arm 35 to the terminal post 38 that a line L through the axis and a switch arm attachment is located substantially half-way between the switch contacts 36 and 37. Accordingly, the shifting of the point of attachment of the U-shaped spring (or springs) 52 to the rocker arm 4l back and forth over this line L causes the U-shaped spring (or springs) 52 to snap the point of attachment of the switch arm (or arms) 55 to the spring (or springs) S2 in the opposite direction over the line L. As a result, a switch arm 35, when shifted, is always caused to effect a quick make or break with the contacts 36 and 37. For reasons that will be explained later, in the adaptation shown in Figs. and 2l the axis of the rocker arm shaft 47 is slightly offset from the line L.

The main cam 42 is in the form of an annular disk which, for all of the adaptations herein shown, except for that shown in Figs. 13-18, is staked to a shaft 56 journaled on the panel E. The periphery of the cam l2 constitutes a cam track S7 which at one point is 'formed with a radially-disposed offset 58 either in the nature of an inwardly-extending recess (see all figures except Figs. 13 and 14) or an outwardly-extending lug (see Figs. 13 and 14). The circumferential dimension of the offset 45, whether it be a depression or an extension, and the nature of the defining walls, against which the cam-track follower pin 47 rides, is varied., depending upon the results that are to be sought in the use of this improved time switch, Generally, the circumferential dimension will be sufficient to permit approximately a maximum fifteen minute defrosting period. Obviously, it could be dimensioned for other maximum periods if required.

For the adaptations shown in Figs. 2 and 3, 8 and 9, and 25, the offset 53 on the main cani 42 is in the form of a recess with the opposed dening walls spaced apart a very short circumferential distance and both curved very slightly away from radial lines, thereby making the action of the rocker arm 41 quite abrupt. For the adaptations shown in Figs. 2O and 2l, the recess defining walls of the oifset 58 are more widely separated circumferentially and more inclined to the radius than in other adaptations. This modication is cam 44 only of the rocker arm 41.

The auxiliary cam is mounted to rotate with an intermediate gear 59 forming a part of the gearing C. This arrangement, is provided to coact with the eccentric offset of the rocker arm stud shaft 47 in order to secure a simultaneous snapping of the pair of switch arms 35 in one direction but to secure successive or sequential snapping of the switch arms in the opposite direction independently of the main cam offset 58, to achieve purposes that will be explained subsequently. An offset 60 on the auxiliary cam 44 is in the form of a recess with the defining walls more widely spaced circumferentially than is the recessed offset 58 in most of the other adaptations. However, the leading edge or face of posed so as to secure an abrupt action of the rocker arm 41 whereas the trailing face of the offset 6ft is curved so as to secure a gradual change in the position of the rocker arm 41 with a consequent successive reversal to normal positions of the two switch arms 35.

required because the auxiliary l, is operative in securing the effective shifting the offset 60 is radially disfill - mediate gear 59 and meshes with For the adaptation shown in Figs. i3 and 14, the offset 53 is in the nature of a projection or tooth. The advancing defining face is inclined or curved, thereby effecting a gradual change in the shifting of the rocker arm 41 whereas the trailing face of the offset 58 in this adaptatio-n is radially disposed, thereby permitting an abrupt shifting of the rocker arm 41 when conditions permit, as will be indicated presently.

The cam shaft 56 which mounts the main cam 42, is formed with a square hub 61 and, in most of the adaptations herein shown, with adjacent cylindrical reduced parts 62 and 63 and is journaled on a stud shaft 64 staked to the mounting E. in Fig. 4, the parts 62 and 63 are shown to be integral whereas in other adaptations (see Fig. 16 for example) the parts 62 and 63 are separately formed and press assembled.

The hub part 61 is recessed at its opposite ends to form noncircular seats for the main cam 4Z and the main gear 65 of the gearing C, which cam 42 and gear 65, in all but the adaptations shown in Figs. 13 to 18, are staked thereon in the conventional manner. In the adaptation shown in these latter figures, the noncircular aperture in the cam 42 is formed slightly larger than the seat on the square hub 61 (see Fig. 17) so as to permit a slight relative angular movement of the cam 42 on the shaft 56, for a reason that will be made clear later. In this adaptation, the cam 42 is held against axial displacement by a washer 66 staked to the shaft hub 61. A spring 80, the ends of which are caught on lugs 42 and 65 of the cam 42 and gear 65 respectively, normally shifts the cam 42 on the shaft 56 clockwise to the limit of its relative movement permitted by the differing dimensions of the aforesaid noncircular cam aperture and shaft seat (see Fig. 17).

The solenoid 43, forming a part of the switch-actuating mechanism B for the adaptation shown in Figs. 13-19, is provided to make the return of the switch means A to its normal position, with the cam-track follower 50 pressed against the cam track 57 of the main cam 42, independent of the action of the offset 5S. The solenoid 43 is positioned on the mounting E with the armature 67 having a shiftable pivotal connection 68 to the rocker arm 41 on the opposite side of the pivot from that whereat the rocker arm is connected to the switch arm 35. As indicated in the circuit diagram of Fig. 19,

the solenoid 43 is connected in series with the defrost accelerating means H and a normally-closed thermostat T arranged in the refrigerator. The solenoid 43, under the influence of the thermostat T, thermally connected to the refrigerator plates, controls the return of the rocker arm 41 to normal position (with the cam-track follower 50 pressing against the cam track 57) which will occur some time after the offset 5S passes the camtrack follower 50.

The gearing C whereby the switch-actuating mechanism B is connected to the motor D comprises the already-mentioned main gear 65, the intermediae gear 59, and pinions 70 and 71. The pinion 70 is driven by the motor D whereas the pinion 71 is fixed on the interthe main gear 65.

The motor D, which drives the switch-actuating mechanism A previously described is a conventional synchronous motor attached to the mounting E by suitable fastening means 69 and connected to drive the pinion 7 t).

The form of the mounting E depends much upon the refrigerator wherewith a time switch embodying this invention is to be used. This is especially influenced by the wiring arrangement for the refrigerator. In certain of the hereinshown adaptations (Figs. 2 to 5 and 2O to 22) the mounting is a rectangular panel 72 formed of suitable insulating material, such as hard rubber or some synthetic substance. As shown in the above figures, all of the parts of the switch and the circuit terminals are mounted on this panel. ln the other adaptations, the

switch means A is mounted on asmall plate 73 formed of suitable insulating material. The plate 73` (or plates, Where two are used) and the other parts of the switch are mounted on a panel 7d generally made of metal. Incidentally, the plate 73 is so designed that one may be used for any of the adaptations employing a single switch means A or two of them may be arranged in reverse relationship (see Fig. 25) for an adaptation eniploying two switch means A.

Generally some form of cover 7S is provided for attachment to the mounting E to enclose all of the abovedescribed means and mechanism. Two forms of such cover 75 are shown (see Figs. l0 and l5). The former is locked in place on the mounting E by bending over tongues 84 under the edge of the panel 7 4. In this adaptation an insulating strip 81 is arranged along the inside of one end of and across the top of the cover adjacent the switch terminals 33, 39, and 40 to protect them against any inadvertent contact with the cover. Also in this adaptation a cap 82 is held in place over the cover opening for the cam shaft 5o by a spring 83 (see Fig. 1l) one end of which spring is seated in an annular groove in the shaft 56.

The other form of cover 75 is secured in place by screws 76 threaded into the posts 77 which are staked to the panel 74 and on the free ends of which posts the top face of the cover 75 rests.

The mounting E, with its cover 75 where used for any of the adaptations herein-shown, is so formed and arranged that this time switch may be secured to the refrigerator housing in the place provided therefor by the manufacturer of the refrigerator. The attachment would be such that a pointer knob 73 on the cam shaft 56 will appropriately register with the scale F (see Fig. l), which scale bears some indicia to represent the major time divisions of a 24-hour period.

Before explaining specifically the operation of this improved time switch, for use in refrigerator defrosting, it should be noted that the essential function of the device is once every 24 hours to cut off the refrigerating mechanism G and cut in the defrost accelerating means, and after a predetermined period of time restore the refrigerating-'nechanism circuit to operative condition and open the contacts leading to the defrost accelerating means. Because that period of time may be greater than is required for effecting the desired defrosting, refrigerators equipped with the herein-described time switch usually will include in the circuit to the defrosting the herein-before mentioned bellows-operated switch.

The bellows-operated switch is thermallyconditioned by the evaporator plates of the refrigerator and is preferably of double throw type having one of its poles connected in the circuit for the refrigerator mechanism and its other pole connected in the circuit of the dcfros't accelerating means. Accordingly, the bellows switch perhaps more often than not may determine the duration of the defrosting period and the idle period for the refrigerating mechanism.

When the refrigerator needs defrosting, the bellows switch will be activated to close the circuit to the defrost accelerating means and hold that circuit closed pending the arrival of this time switch at the defrostng period. When the time switch reaches that point, the shifting of the switch means A will cut out the refrigerating-mechanism circuit and cut in the defrost accelerating means circuit. lf the time required for effective defrosting is less than the maximum interval for which this time switch is constructed to reverse the operative condition of the aforesaid circuits, the bellows switch will be activated by the temperature of the evaporator plates to open the circuit to the defrost accelerating means and close the circuit to the refrigerating mechanism. Thus, there will be no idleness of the refrigerating mechanism beyond the period required for effective defrosting. When the time switch reaches the end of the period for Si which it is constructed to reverse the operative condition of the aforesaid circuits, the switch means A will be restored to its normal condition and the influence of the bellows switch on the refrigerating mechanism will be neutralized.

lf, perchance, the defrost accelerating means circuit is not opened by the bellows switch as just noted, before the time switch reaches the end of the period for which it was constructed to reverse the operative condition of the aforesaid circuits, then the time switch will cause the normal restoration of the aforesaid circuits, cutting out the defrost accelerating means and cutting in the refrigerating mechanism.

When a refrigerator equipped with one of the hereindescribed time switches is installed and operatively con nested with the house circuit, the pointer knob 78 is turned clocswise (see Fig. l) to so register with the surrounding dial as to correspond with the time of the day at which the connection to the house circuit is made. The synchronous motor will begin to operate and by virtue of its construction will automatically function to effect a defrosting period at about 2:00 a. m. each day thereafter.

If for any reason it were desired to have the defrosting occur at some time other than 2:00 a. m., itA would be necessary only to turn the pointer knob 73 with respect to the surrounding dial the same number of hours in advance of the then time of day as it is desired to delay the defrost period after 2:00 a. m.

During the operation of the time switch the rocker arm 41 is held by the spring 48 to press the cam-track follower pin Si? into contact with the cam track 57, except during the brief defrosting periods. The switch means A is thereby positioned to maintain closed the circuit to the refrigerating mechanism G and hold open the circuit to the defrost accelerating means H or H. As the time arrives for initiating defrosting the oset 58 moves into registration with the cam-track follower pin 50 resulting in a reverse of these circuits.

In the adaptation shown in Figs. l to 5, 8 to il, and 25 to 27, there is a practically' instantaneous drop of thc follower pin 50 into the depression 55. The consequent oscillation of the roclier arm 41 shifts the connection thereof to the lJ-s'naped spring 52, over the line L resulting in a snap reverse movement of the connection of the U-suaped spring 52 to the switch arm 35. A quick make and break of the switch arm 35 with the respective contacts 36 and occurs, cutting out the circuit to the refrigerating mechanism G and cutting in the circuit to the defrost accelerating means H.

In the adaptation shown in Figs. i3 to 19, the initial contact of the offset projection 58 with the cam-track follower 5b is taken up in the lost motion mounting of the cam 552 and results in the cam 42 being heid stationary as the shaft 56 continues its rotation. The limit of such relative rotation is reached when the rounded corners of the shaft huo part comes into Contact with the walls of the noncircular aperture the cam i2 (the reverse of 'Fim 17). Thereupon the cam 42 is forced to continue its rotation with the shaft S, the follower 59 meanwhile riding up the adva cing inclined face of the offset 5S. When the follower 50 is about half-way up this inclined face', the rocker arm il is shifted sufficiently to reverse the position oit' the switch arm 35 as just explained.

The thermostat bellows operated switch T being connected to the refrigerator pl' 'es and normally closed, this snapping of the switch arm 35 energizes the solenoid 33 causing it to shift the rocker -rm the remainder of its permissibie swing and thereby releasing the cam 42 to assume its normal position on the shaft 56 as biased by the spring Si). The solenoid 43 will hold the rocker arm di in this retracted position until thev temperature of the refrigerator plates is such as to cause the thermostat T to open the circuit including avoaalii such thermostat and the heating element H. The rocker arm 41 thereupon is released and the switch means A shifted to close the refrigerator mechanism circuit.

The reason for the lost motion mounting in this adaptation is to insure the immediate retraction of the cam projection 58 from the normal path of the follower pin 50 so that if, at the time of the reverse of the switch means A, the thermostat T is open-thus requiring no defrost period for the refrigeratorthe follower pin 50 may return to contact with the cam track 51 thereby maintaining closed the refrigerator mechanism circuit.

In the adaptation shown in Figs. -24 the axis of the rocker arm stud shaft d'7 is offset from the line L through the switch arm mountings and the action of the main cam 42 is so coordinated with the auxiliary cam 44 as to provide a switch which will meet the requirements of a particular refrigerator manufacturer who requires a delay in the closing of the refrigerator mechanism circuit after the cut off of the circuit for the defrost accelerating means. The exact instant when the shift of the rocker arm 41 occurs to reverse the normal condition of the two circuits depends not only upon the registration of the cam-track follower pin 59 with the offset 58 in the main cam i2 but upon a simultaneous registration of the offset 60 in the auxiliary cam 44 with the camtrack follower pin 51. When these are concurrent, the rocker arm il is released to effect a simultaneous sudden shifting of the two switch arms 35. As with the other adaptations previously explained, the circuit to the refrigerating mechanism is thereupon cut off and the crcuit to the defrost accelerating means H is cut in. As the cam ed rotates to bring the curved advancing face of the offset of) into contact with the cam-track follower 51, the rocker arm 4l is gradually swung toward its normal position for actuating the switch means A to restore the operative condition of the circuit to the refrigerating mechanism G. As the connection of the U-shaped spring 52 to the rocker arm 41 passes the line L for the left-hand switch means A, the switch arm 3S is reversed in the manner already explained. As an examination of the wiring diagram (Fig. 24) will reveal, this will cut out the defrost accelerating means H, in the event that the circuit has not already been opened by the bellows operating switch. However, because of the slight offset of the axis of the rocker arm pivot from the line L, the passing of the connection of the U-shaped spring 52 at the opposite end of the rocker arm over the line L is delayed for several minutes as the follower pin 51 continues its ascent of the trailing, curved, defining face of the offset 60. After some further shift of the rocker arm 41, the right-hand switch arm 35 for the other switch means A is snapped and the circuit restored to the refrigerating mechanism G.

In the adaptation shown in Figs. -28, the circuits are arranged (as Fig. 2S clearly indicates) so that the circuit to the compressor of the refrigerating mechanism G is maintained closed but the cold-control means is cui out at the time that the rocker arm 41 is shifted to cui in the circuit to the solenoid-operated valve H.

Where the two switch means A are used (Figs. 20-28) one each of the contacts are dead, as the circuit diagrams clearly indicate.

If at any time this improved switch and the conventional bellows switch should fail, and result in the defrosting heating coil remaining on materially longer than is required, the thermal overload switch would be activated to cut out the defrosting circuit altogether', in which case there would be no further automatic defrosting until the situation were remedied.

Other variations and modifications in the details of the structure and arrangement of the parts may be resorted to within the spirit and coverage of the appended claims.

We claim:

1. In a time switch, the combination of a motor-driven cam having a track with an abrupt radial offset, the motor drive of said cam causing said cam to rotate with a substantially xed time cycle, a switch arm mounted for movement into and out of engagement with a contact, a rocker arm normally urged to engage said cam track to be oppositely shifted by said offset, resilient means so connected to said rocker arm and to said switch arm that the opposite shifting of said rocker arm by said camtrack offset snaps the connections of said means to said arms oppositely back and forth over a line through the axis of said rocker arm pivot and the mounting of said switch arm to effect a quick make and break of said switch arm with said contact, and electrically energized means auxiliary to and actuatable independently of said cam offset operative to make the movement of said rocker arm in one direction independent of said cam offset during variable portions of the time cycle of said cam, either while the cam is rotating through a fraction of a revolution or through one or more revolutions.

2. In a time switch, the combination of a motor-driven cam having a track with an abrupt radial offset, said cam rotating with a substantially predetermined time cycle a switch arm mounted for movement into and out of engagement with a contact, a rocker arm separately mounted from said switch arm so as to be capable of rocking movement relatively to said switch arm, said rocker arm being normally urged to engage said cam track to be oppositely shifted by said offset, resilient means so connected to said rocker arm and to said switch arm that the opposite shifting of said rocker arm by said cam-track offset snaps the connections of said means to said arms oppositely back and forth over a line through the axis of said rocker arm pivot and the mounting of said switch arm to effect a quick make and break of said switch arm with said contact, a variable control device, and means responsive to said variable control device operatively connected to said rocker arm and actuated independently of said cam offset for making the movement of said rocker arm in one direction independent of said cam track over variable intervals established by said variable control device ranging from a fraction of a revolution to one or more revolutions of said cam.

3. In a time switch, the combination of a motor-driven cam having a track with an abrupt radial offset, a switch arm having one end mounted on a stationary support and having its other end arranged for movement into and out of engagement with a stationary contact, a rocker arm separately mounted from said switch arm so as to be capable of limited rocking movement relatively thereto, said rocker arm being normally urged to engage said cam track to be oppositely shifted by said offset, resilient means so connected to said rocker arm and to said switch arm that the opposite shifting of said rocker arm by said cam-track offset snaps the connections of said means to said arms oppositely back and forth over a line through the axis of said rocker arm pivot and the mounting of said switch arm to effect a quick make and break of said switch arm with said contact, and an electrically energized solenoid connected to said rocker arm and capable of being energized at any time independently of the time cycle of said cam offset for making the movement of said arm in one direction temporarily independent of said cam offset.

4. In a time switch, the combination of a motor, a pair of switches, a pair of cams each having tracks with opposed circumferentially spaced oppositely extending radial offsets one of which offsets on one of said cams is abrupt and the other of which is gradual, a rocker arm connected to actuate said switches and normally urged to press cam-track followers on said rocker arm into contact with said cam tracks to effect an opposite shifting of said rocker arm by said offsets to actuate said switches, and gearing interposed between said motor and said cams to drive said cams at relatively different predetermined speeds whereby said cam offsets are brought into frequent simultaneous registration with said lcam-track followers to permit said abrupt offset on said one cam to effect a sudden simultaneous shifting of said switches in one direction and permit said gradual offset to effect a successive shifting of said switches in the opposite direction.

5. In a time switch, the combination of a motor, a pair of cams driven by said motor at different correlated speeds, each of said cams having tracks with opposed circumferentially-spaced oppositely-extending radial offsets one of which offsets on one of said cams is abrupt and the other of which is gradual, a pair of opposed and alined switch arms each mounted for movement toward and away from a contact, a rocker arm interposed between said switch arms with the pivot of said rocker arm located adjacent the plane common to the mountings of said switch arms, resilient means normally urging said rocker arm to hold one of said cam-track followers on said rocker arm against the respective cam for opposite shifting by the cam offsets thereon when the other cam track is in registration with the respective cam track offset, and other resilient means so connected to opposite parts of said rocker arm and to the respectively adjacent switch arms that the opposite shifting of said rocker arm by said cam offsets snaps the connections of said other resilient means to said arms oppositely back and forth over said plane to effect a quick make and break of said d switch arms with their respective contacts, the shift of said rocker arm in one direction being effected by said abrupt offset to cause a substantially simultaneous change of said switch arms and in the opposite direction being effected by said gradual offset to cause a sequential change in said switches.

6. In a time switch, the combination of a motor-driven shaft, a cam fixed to rotate with said shaft but having a limited angular movement relative thereto, said cam having a track with an offset one face of which is inclined to the radius of said cam, resilient means normally urging said cam toward one limit of its angular movement relative to said shaft, a switch arm mounted for movement between spaced contacts, a rocker arm normally urged to press a cani-track follower thereon into contact with said cam track whereby engagement of said follower with said inclined offset face rst effects the permitted limited relative angular movement of said cam followed by a subsequent shifting of said rocker arm, the passing of said cam track follower from said inclined face causing the restoration of the normal angular relationship of said cam and shaft and the release of said rocker arm, and resilient means so connected to said rocker arm and to said switch arm that the opposite shifting of said rocker arm by said cam-track offset snaps the connections of said means to said arms oppositely back and forth over a line through the axis of said rocker arm pivot and the mounting of said switch arm to effect a quick make and break of said switch arm with said contacts.

7. ln a time switch, the combination of a motor-driven shaft, a cam on said shaft, lost motion driving means for driving said cam from said shaft permitting limited angular movement of said cam relatively to said shaft, said cam having a track with an offset one face of which is inclined to the radius of said cam, resilient means normally urging said cam toward one limit of its angular movement relative to said shaft, a switch arm mounted for movement between spaced contacts, a rocker arm normally urged to press a cam-track follower thereon into contact with said cam track whereby engagement of said follower with said inclined offset face first effects the permitted limited relative angular movement of said cam follower by a subsequent shifting of said rocker arm, the passing of said cam-track follower from said inclined face causing the restoration of the normal angular relationship of said cam and shaft and the release of said rocker arm, resilient means so connected to said rocker arm and to said switch arm that the opposite shifting of said rocker arm by said cam-track offset snaps the connections of said means to said arms oppositely back and forth over a CII line through the axis of said rocker arm pivot and the mounting of said switch arm to effect a quick make and break of said switch arm with said contacts, and a solenoid connected to said rocker arm and adapted to be controlled independently of said cam offset for temporarily holding said rocker arm in its retracted position after release from said cam offset.

8. In a time switch, the combination of a motor-driven cam having a track with an abrupt radial offset, a pair of opposed and alined switch arms each mounted for movement toward and away from a contact, a rocker arm interposed between said switch arms with the pivot of said rocker arm located substantially in a plane through the mountings of said switch arms, means normally urging said rocker arm to press a cam-track follower thereon into Contact with said cam track for opposite shifting of said rocker arm by said cam offset, and resilient means so connected to the opposite ends of said rocker arm and the opposed switch arms that the opposite shifting of said rocker arm by said cam oset snaps the connections of said resilient means to said arms oppositely back and forth over said plane to effect a quick make and break of said switch arms with their respective contacts.

9. In a refrigerator defrosting switch, the combination of a motor-driven cam having an annular track with an abrupt radial offset, a switch arm mounted for movement between spaced contacts and coacting to control the alternate operation of refrigerating mechanism and electrically heated defrosting means for the refrigerator, a stationary pivot adjacent to said motor-driven cam, a bell-crank rocker arm rotatably mounted on said pivot and normally urged to press a follower on said rocker arm to engage said cam track, resilient means so connecting said rocker arm to said switch arm that the opposite shifting of said rocker arm by said cam-track offset snaps the connections of said resilient means to said switch arm and to said rocker arm oppositely back and forth over a line through the axis of said rocker arm pivot and the mounting of said switch arm to effect a quick make'and break of said switch arm with said contacts, and thermostatically-actuated means connected to said rocker arm and controlled by the temperature in the refrigerator for making the movement of said rocker arm in one direction temporarily independent of said cam offset for a variable interval of time which is governed solely by the refrigerator temperature independently of the rotative movement of said cam.

l0. The combination with a refrigerator having a temperature-controlled cold-creating mechanism and electrically heated defrost accelerating means wherein the mechanism and means are connected in separate electrical circuits with a thermostat interposed in the electrically heated defrost accelerating means circuit, of a switch mechanism for controlling said separate circuits and comprising, a motor-driven cam having an annular track with an abrupt radial offset, a pivot adiaccnt to said cam, a rocker arm pivotally mounted on said pivot and comprising a cam follower which is normally urged to engage the annular track of said cam, a switch arm mounted for movement between spaced contacts to coact therewith to control said circuits for effecting the alternative operation of said refrigerating mechanism and said defrost accelerating means, resilient means, connections between said resilient means and said rocker arm and said switch arm so that the opposite shifting of said rocker arm by said cam-track offset snaps the connections of said resilient means to said arms oppositely back and forth over a line through the axis of said rocker arm pivot and the s mounting of said switch arm to eect a quick make and break of said switch arm with said contacts, and a soienoid connected to said rocker arm and series with said thermostat whereby said rocker arm return from retraction by said offset is made temporarily independent thereof,

l1. In a time switch of the class described, the combination of, a motor-driven cam having an annular track with an abrupt radial offset, a pair of opposed and alined switch arms each mounted for movement toward and away from a cooperating relatively stationary Contact, a rocker arm interposed between said switch arms, a pivot for said rocker arm, biasing means normally urging said rocker arm around said pivot to press a camtrack follower thereon against said cam track for opposite shifting by said cam offset, and resilient means and cooperating connections so connected to the opposite portions of said rocker arm and the respectively adjacent switch arms that the opposite shifting of said rocker arm by said cam offset snaps the said connections of said resilient means to said arms oppositely back and forth across a plane common to the mountings of said switch arms, said rocker arm pivot being so disposed with respect to said plane as to cause the simultaneous shifting of said switch arms.

l2. The combination with a refrigerator having a temperature-controlled cold-creating mechanism and a dcfrost accelerating means wherein the mechanism and means are connected in separate electrical circuits, of a switch mechanism for controlling said separate circuits and comprising, a motor-driven cam having an annular track with an abrupt radial offset, a pair of opposed and alined switch arms each mounted for movement toward and away from a contact one of which contacts is interposed in one of said circuits and the other of which contacts is interposed in the other of said circuits, a rocker arminterposed between said switch arms, a pivot for said rocker arm, biasing means normally urging said rocker arm to press a cam-track follower thereon against said cam track for opposite shifting by said cam olfset, and resilient means and cooperating connections so connected to the opposite portions of said rocker arm and the respectively adjacent switch arms that the opposite shifting of said rocker arm by said cam offset snaps the said connections of said resilient means to said arms oppositely back and forth across a plane common to the mountings of said switch arms, said rocker arm pivot being so disposed with respect to said plane as to cause the sequential shifting of said switch arm-s at least' in one direction, whereby a substantially predetermined period of delay follows the cle-energization of said defrost accelerating means by said switch mechanism before said temperature controlled cold-creating mechanism is again energized.

13. ln a time switch, the combination of a time driven shaft, a cam on said shaft, lost motion driving means for driving said cam from said shaft permitting limited angular movement of said cam relatively to said shaft, cam follower means responsive to said cam, switch means responsive to said cam follower means, electromagnetic means responsive to said switch means and operative to hold said cam follower means in its actuated position after actuation by said cam, and spring means acting on said cam to impart a snap motion thereto in a forward direction, permitted by said lost motion driving means, as soon as said electromagnetic means is energized.

14. In a time switch of the class described, the conibination of a cam, a synchronous motor connected to drive said cam with a substantially fixed time cycle, said cam having an outer peripheral track provided with a relatively abrupt radial offset, a switch arm mounted for movement into and out of engagement with a relatively stationary contact, a rocker arm, a pivot pin for said rocker arm defining a pivotal axis therefor which is disposed approximately in a straight line extending substantially in prolongation of said switch arm when the latter is substantially midway between its extreme positions, a cam follower on said rocker arm riding on the outer peripheral track of said cam, a torsion spring exerting a constant torsion on said rocker arm for holding said cam follower pressed continuously against said cam track, and an over-center snap-spring operatively connected between said switch arm and said rocker arm so that the opposite shifting of said rocker arm by said cam track offset transmits an over-center snap action to said switch arm by opposite movement of the opposite ends of said snapspring back and forth across said substantially straight line extending substantially in prolongation of said switch arm and through the pivotal axis of said rocker arm, said torsion spring exerting a greater torsional force in the direction for holding the cam follower of the rocker arm pressed against said cam track than said snapspring can exert in the opposite direction tending to lift said cam follower from said cam track.

15. In a time switch of the class described, the combination of a cam, a synchronous motor connected to drive said cam with a substantially fixed time cycle, said cam having an outer peripheral track provided with a relatively abrupt radial offset, a pair of opposed and aligned switch arms each mounted for movement toward and away from a cooperating relatively stationary contact, a rocker arm interposed between said switch arms. a pivot pin for said rocker arm defining a pivotal axis therefor which is disposed in close proximity to a plane common to the mountings of said switch arms, a cam follower on said rocker arm riding on the outer peripheral track of said cam, a rocker actuating spring exerting a constant torsion on said rocker arm for holding said cam follower pressed against said cam track, and over-center snap-springs operatively connected between said switch arms and adjacent portions of said rocker arm so that opposite shifting of said rocker arm by said cam track offset and Said rocker arm spring transmits over-center snap actions to said switch arms by opposite movement of the opposite ends of said snap springs back and forth across the said plane common to the mountings of said switch arms, said rocker arm pivot being so disposed with respect to said plane as to cause said switch arms to be actuated in sequence at least in one direction for securing a time delay interval between the actuation of one of said switch arms and the actuation of the other switch arm in the same direction of movement of said rocker arm.

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